"I started using [Diamax] daily in September and instantly noticed a difference. It creates a healthy scalp which promotes healthy hair," Minnillo told Us in NYC December 8. "Literally you just part your hair, spray it at the roots and part it again. You probably use 10-15 sprays on your hair, max, then you can flip your hair and blow it out or style it however."

"I use it on all my clients, because it's not just for those with thin hair -- it protects the hair as well," her hairstylist, Betsy Reyes, weighed in. "It's soft so you don't have that sticky of flaky element to it. You can use it on wet or dry hair. It's a unisex product."

Head to nioxin.com to learn more about Lachey and Reyes' favorite hair product.